Add user action for changing the active window in Ash overview mode

ash/wm/overview/window_selector_controller.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/wm/overview/window_selector_controller.h"
 
 #include <vector>
 
 #include "ash/metrics/user_metrics_recorder.h"
 #include "ash/root_window_controller.h"
 #include "ash/session/session_state_delegate.h"
 #include "ash/shell.h"
 #include "ash/system/tray/system_tray_delegate.h"
 #include "ash/wm/mru_window_tracker.h"
 #include "ash/wm/overview/window_selector.h"
 #include "ash/wm/window_state.h"
 #include "ash/wm/window_util.h"
 #include "base/metrics/histogram.h"
 #include "ui/aura/window.h"
 
 namespace ash {
 
-WindowSelectorController::WindowSelectorController() {
+WindowSelectorController::WindowSelectorController()
+    : initially_active_window_(nullptr) {
 }
 
 WindowSelectorController::~WindowSelectorController() {
 }
 
 // static
 bool WindowSelectorController::CanSelect() {
   // Don't allow a window overview if the screen is locked or a modal dialog is
   // open or running in kiosk app session.
   return Shell::GetInstance()->session_state_delegate()->
@@ skipping 16 matching lines @@
         ash::Shell::GetInstance()->mru_window_tracker()->BuildMruWindowList();
     auto end =
         std::remove_if(windows.begin(), windows.end(),
                        std::not1(std::ptr_fun(&WindowSelector::IsSelectable)));
     windows.resize(end - windows.begin());
 
     // Don't enter overview mode with no windows.
     if (windows.empty())
       return;
 
+    OnSelectionStarting();
     Shell::GetInstance()->OnOverviewModeStarting();
     window_selector_.reset(new WindowSelector(this));
     window_selector_->Init(windows);
     OnSelectionStarted();
   }
 }
 
 bool WindowSelectorController::IsSelecting() {
   return window_selector_.get() != NULL;
 }
 
 bool WindowSelectorController::IsRestoringMinimizedWindows() const {
   return window_selector_.get() != NULL &&
          window_selector_->restoring_minimized_windows();
 }
 
 // TODO(flackr): Make WindowSelectorController observe the activation of
 // windows, so we can remove WindowSelectorDelegate.
 void WindowSelectorController::OnSelectionEnded() {
   window_selector_->Shutdown();
   window_selector_.reset();
   last_selection_time_ = base::Time::Now();
   Shell::GetInstance()->OnOverviewModeEnded();
+
+  // Record UMA_WINDOW_OVERVIEW_ACTIVE_WINDOW_CHANGED if the active window
+  // is different from the window that was active upon entering overview
+  // mode.
+  aura::Window* active = wm::GetActiveWindow();

[bruthig, 2015/05/12 17:37:38]

I feel like this metric should only be recorded if the window change was
actually due to someone selecting a window from the WindowSelector UI.

I'm concerned that the |active| window here could be set by a different task
switching mechanism (ie alt+tab or clicking a docked window) and that this
metric will be double counted in the those two buckets.

[oshima, 2015/05/12 20:25:13]

This may also change if the window is closed or an app requested focus
explicitly. It's probably rare, and I don't have strong opinion here so let me
know when both of you agreed, and I'll review again.

[tdanderson, 2015/05/14 01:36:32]

In patch set 2 the user action won't be recorded when closing windows in
overview mode. It will still be recorded if a window requests focus
programmatically, but that is rare and Ben and I have agreed we can live with
having that small amount of noise in the data.

+  if (initially_active_window_ && active &&
+      active != initially_active_window_) {
+    Shell::GetInstance()->metrics()->RecordUserMetricsAction(
+        UMA_WINDOW_OVERVIEW_ACTIVE_WINDOW_CHANGED);
+  }
+  initially_active_window_ = nullptr;
+}
+
+void WindowSelectorController::OnSelectionStarting() {

[bruthig, 2015/05/12 17:37:38]

It would be less invasive to WindowSelectorController and would allow the future
work for the catch-all TaskChanged metric to be centralized if
OnSelectionStarting, OnSelectionStarted, OnSelectionEnding and OnSelectionEnded
were events that a WindowSelectorObserver.

It is worth considering but may be too risky this close to branch cut.

[tdanderson, 2015/05/14 01:36:32]

Not pursuing this as per in-person discussion.

+  aura::Window* active = wm::GetActiveWindow();
+  if (active && WindowSelector::IsSelectable(active))
+    initially_active_window_ = active;
 }
 
 void WindowSelectorController::OnSelectionStarted() {
   if (!last_selection_time_.is_null()) {
     UMA_HISTOGRAM_LONG_TIMES(
         "Ash.WindowSelector.TimeBetweenUse",
         base::Time::Now() - last_selection_time_);
   }
 }
 
 }  // namespace ash